How do I connect these faces up without adding too many quads using retopology?
Hi, this is the "usual" workflow how to proceed from a low-poly to high-poly (or vice-versa) and keeping quads - You could repeat the process multiple times so there is no problem to start with 2 quads and finish with 8 or more. Try it if it will work for You cause I dunno how "dense" your original mesh is so maybe this could not fit properly (too many steps needed).

Hope it helps, Buddy.

Sincerely, Jan